2. Who Am I?
Miguel has over 10 years of experience with
Microsoft Technologies. Specialized with many
things in the Microsoft ecosystem, including C#,
F#, and Azure, he likes to blog about his
engineering notes and technology in general. He
is also very involved in the Montréal msdevmtl
community where he is a co-organizer.
NEXUS INNOVATIONS - PRÉSENTATION 2
https://blog.miguelbernard.com
https://www.linkedin.com/in/miguelbernard/
@MiguelBernard88
https://github.com/mbernard
3. New features
• Readonly members
• Default interface methods
• Pattern matching enhancements
• Using declarations
• Static local functions
• Disposable ref structs
• Nullable reference types
• Asynchronous streams
• Indices and ranges
• Null-coalescing assignment
• Unmanaged constructed types
• Stackalloc in nested expressions
• Enhancement of interpolated verbatim strings
NEXUS INNOVATIONS - PRÉSENTATION 3
4. Nullable reference types
To enable it
• In .csproj
• <LangVersion>8.0</LangVersion>
• <Nullable>Enable</Nullable>
• In code
• #nullable enable
• #nullable restore
NEXUS INNOVATIONS - PRÉSENTATION 4
7. Pattern matching enhancements
Use case of a Toll service
V1 -Price per vehicle type
• 🚗Car -> 2$
• 🚕Taxi -> 3.50$
• 🚌Bus -> 5$
• 🚚Truck -> 10$
NEXUS INNOVATIONS - PRÉSENTATION 7
8. Pattern matching enhancements
V2 - Price considering occupancy
• Car and taxi
• No passengers -> +0.50 $
• 2 passengers -> -0.50 $
• 3 or more passengers -> -1$
NEXUS INNOVATIONS - PRÉSENTATION 8
9. Pattern matching enhancements
V3 - Price considering occupancy
• Car and taxi
• No passengers -> +0.50 $
• 2 passengers -> -0.50 $
• 3 or more passengers -> -1$
• Bus
• Less than 50% full -> +2$
• More than 90% full -> -1$
NEXUS INNOVATIONS - PRÉSENTATION 9
12. Asynchronous streams
To have an async stream you need 3 properties
• It’s declared with the ‘async’ modifier
• It returns an IAsyncEnumerable<T>
• The method contains ‘yield return’ statements
NEXUS INNOVATIONS - PRÉSENTATION 12
13. Asynchronous streams
NEXUS INNOVATIONS - PRÉSENTATION 13
internal async IAsyncEnumerable<int> GenerateSequence()
{
for (int i = 0; i < 20; i++)
{
// every 3 elements, wait 2 seconds:
if (i % 3 == 0)
await Task.Delay(3000);
yield return i;
}
}
internal async Task<int> ConsumeStream()
{
await foreach (var number in GenerateSequence())
{
Console.WriteLine($"The time is {DateTime.Now:hh:mm:ss}. Retrieved {number}");
}
return 0;
}
14. Indices and ranges
New operators
• The index from end operator ^, which specifies that an index is relative to the
end of the sequence
• The range operator .., which specifies the start and end of a range as its
operands
NEXUS INNOVATIONS - PRÉSENTATION 14
15. Indices and ranges
Notes
• The ^0 index is the same as sequence[sequence.Length].
• Note that sequence[^0] does throw an exception, just as
sequence[sequence.Length] does
• For any number n, the index ^n is the same as sequence.Length – n
• The range [0..^0] represents the entire range, just as [0..sequence.Length]
represents the entire range.
NEXUS INNOVATIONS - PRÉSENTATION 15
16. Indices and ranges
NEXUS INNOVATIONS - PRÉSENTATION 16
private string[] words = new string[]
{
// index from start index from end
"The", // 0 ^9
"quick", // 1 ^8
"brown", // 2 ^7
"fox", // 3 ^6
"jumped", // 4 ^5
"over", // 5 ^4
"the", // 6 ^3
"lazy", // 7 ^2
"dog" // 8 ^1
};
17. Indices and ranges
NEXUS INNOVATIONS - PRÉSENTATION 17
var allWords = words[..]; // contains "The" through "dog".
var firstPhrase = words[..4]; // contains "The" through "fox"
var lastPhrase = words[6..]; // contains "the, "lazy" and "dog"
var lazyDog = words[^2..^0];
Index the = ^3;
words[the];
Range phrase = 1..4;
words[phrase];
19. Static local functions
NEXUS INNOVATIONS - PRÉSENTATION 19
int M()
{
int y = 5;
int x = 7;
return Add(x, y);
static int Add(int left, int right) => left + right;
}
You can now add the static modifier to local functions to ensure that local function doesn't capture (reference) any
variables from the enclosing scope.
Doing so generates CS8421, "A static local function can't contain a reference to <variable>."
20. Null-coalescing assignment
C# 8.0 introduces the null-coalescing assignment operator ??=. You can use
the ??= operator to assign the value of its right-hand operand to its left-hand
operand only if the left-hand operand evaluates to null.
NEXUS INNOVATIONS - PRÉSENTATION 20
List<int> numbers = null;
int? a = null;
(numbers ??= new List<int>()).Add(5);
Console.WriteLine(string.Join(" ", numbers)); // output: 5
numbers.Add(a ??= 0);
Console.WriteLine(string.Join(" ", numbers)); // output: 5 0
Console.WriteLine(a); // output: 0
21. Using declarations
Using variables are automatically disposed at the end of the current scope
NEXUS INNOVATIONS - PRÉSENTATION 21
public void Method()
{
using var file = new StreamWriter(“myFile.txt”);
…logic here…
} // Disposed here
public void Method()
{
using(var file = new StreamWriter(“myFile.txt”))
{
…logic here…
} // Disposed here
}
22. Enhancement of interpolated verbatim strings
Order of the $ and @ tokens in interpolated verbatim strings can be any: both
$@"..." and @$"..." are valid interpolated verbatim strings
In earlier C# versions, the $ token must appear before the @ token
NEXUS INNOVATIONS - PRÉSENTATION 22
23. Readonly members
• Only applicable for struct
• Advantages
• The compilier can now enforce your
intent
• Doing so will enable to compiler to
perform performance optimizations on
your code
NEXUS INNOVATIONS - PRÉSENTATION 23
public struct Point
{
public double X { get; set; }
public double Y { get; set; }
public readonly double Distance =>
Math.Sqrt(X * X + Y * Y);
public readonly override string ToString() =>
$"({X}, {Y}) is {Distance} from the origin";
}
24. Unmanaged constructed types
NEXUS INNOVATIONS - PRÉSENTATION 24
public struct Coords<T> where T : unmanaged
{
public T X;
public T Y;
}
Span<Coords<int>> coordinates = stackalloc[]
{
new Coords<int> { X = 0, Y = 0 },
new Coords<int> { X = 0, Y = 3 },
new Coords<int> { X = 4, Y = 0 }
};
25. Stackalloc in nested expressions
Starting with C# 8.0, if the result of a stackalloc expression is of the Span<T>
or ReadOnlySpan<T> type, you can use the stackalloc expression in other
expressions
NEXUS INNOVATIONS - PRÉSENTATION 25
Span<int> numbers = stackalloc[] { 1, 2, 3, 4, 5, 6 };
var ind = numbers.IndexOfAny(stackalloc[] { 2, 4, 6 ,8 });
Console.WriteLine(ind); // output: 1
26. Disposable ref structs
A struct declared with the ref modifier may not implement any interfaces and so
can't implement IDisposable.
Therefore, to enable a ref struct to be disposed, it must have an accessible
`void Dispose()` method. This feature also applies to readonly ref struct
declarations.
NEXUS INNOVATIONS - PRÉSENTATION 26
ref struct Book
{
public void Dispose()
{
}
}
Ca deviant tres interessant quand on a plusieurs using de suite
A generic struct may be the source of both unmanaged and not unmanaged constructed types. The preceding example defines a generic struct Coords<T> and presents the examples of unmanaged constructed types. The example of not an unmanaged type is Coords<object>. It's not unmanaged because it has the fields of the object type, which is not unmanaged. If you want all constructed types to be unmanaged types, use the unmanaged constraint in the definition of a generic struct: